Codeforces Round #506 (Div. 3), problem: (C) Maximal Intersection

#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization ("unroll-loops")

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define pii pair<int,int>
#define pli pair<long long int,int>
#define pbi pair<bool,int>
#define pob pop_back
#define all(a) a.begin(),a.end()
#define fio ios_base::sync_with_stdio(false); cin.tie(0);cout.tie(0);
#define i64 long long int
#define mem(x,y) memset(x,y,sizeof(x))
#define fill(arr,b) fill(arr, arr+sizeof(arr)/sizeof(arr[0]), b)
#define maxarr(n,arr,m) m =-1e9;for(int i=0;i<n;i++)if(arr[i]>m) m=arr[i];
#define read freopen("input.txt","r",stdin);

const double pi = acos(-1.0);
const int maxn = (i64)1e9+7;
#define sz 300005
int l[sz],r[sz];
pair<int,int>pre[sz],suf[sz];
int main()
{
    int n;
    cin >> n;
    for(int i = 0 ; i<n ; i++)cin >> l[i] >> r[i];
    pre[0].first = suf[n].first = 0;
    pre[0].second = suf[n].second = maxn;

    for(int i = 0 ; i<n ; i++)
    {
        pre[i+1].first = max(l[i],pre[i].first);
        pre[i+1].second = min(r[i],pre[i].second);
    }

    for(int i = n-1 ; i>=0 ; i--)
    {
        suf[i].first = max(l[i],suf[i+1].first);
        suf[i].second = min(r[i],suf[i+1].second);
    }
    int ans=0;
    for(int i = 0 ; i<n ; i++)
    {
        ans = max(ans,min(pre[i].second,suf[i+1].second)-max(pre[i].first,suf[i+1].first));
    }
    cout << ans;

    return 0;
}